Electrical and Lightning Injuries - Lightning Injury Research Program

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Electrical and Lightning Injuries
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ELECTRICAL AND LIGHTNING INJURIES
Mary Ann Cooper
Timothy G. Price
PERSPECTIVE
Electrical Injury
Injuries from artificial electricity have been reported for almost 300 years. The
first recorded death caused by electrical current from an artificial source was
reported in 1879, when a carpenter in Lyons, France, inadvertently contacted a
250-volt AC generator.1 The first U.S. fatality occurred in 1881, when a local
inebriate, Samuel W. Smith, passed out on a similar generator in front of a crowd
in Buffalo, New York. The apparent painlessness of his death impressed the
crowd, and electrocution became considered a “humane” mode of execution. In
1890 William Kemmeler was the first man to be put to death in New York
State’s electric chair.2
Electrical burns account for 4% to 6.5% of all admissions to burn units in the
United States and for approximately 1000 fatalities per year in the United
States.3 Most electrical fatalities and adult admissions to burn centers from
electrical injury are occupationally related. Children have a predisposition to
injuries from low-voltage sources, such as electric cords, because of their limited
mobility within a relatively confined environment.4 During adolescence, however,
a more active exploration of the environment is possible and may lead to more
severe high-voltage injuries or death.
At the time of presentation, documentation of injuries is important not only for the
immediate resuscitation of the victim but also medicolegally. Nearly all cases of
electrical injuries eventually involve litigation for negligence, product liability, or
worker compensation.
Lightning Injury
Since no agency requires the reporting of lightning injuries and because many
victims do not seek treatment at the time of their injury, the incidence of injury
and death from lightning is unknown. In the United States, nearly 7000 deaths
were reported in a 34-year period ending in 1974.5 Fewer than 2000 deaths
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Electrical and Lightning Injuries
were reported in a 17-year study ending in 1986.6 Currently it is estimated that
lightning causes 50 to 300 deaths per year in the United States, with four to five
times as many victims suffering non-lethal injuries.5, 6 In typical years, lightning
kills more people in the United States than any other natural disaster except flash
floods and is consistently among the top four weather-related killers.7 Lightning
incidents are most common in locations where there are more thunderstorms,
namely in the South, in the Rockies, along the Atlantic Coast, and in the Hudson,
Ohio, and Mississippi river valleys.
Certain snowy conditions can also result in lightning and thus put skiers at risk for
lightning injury. The formation of sleet and graupel (a type of frozen precipitation
sometimes referred to as snow pellets or soft hail) may indicate the presence of
large differences in electrical potential in the atmosphere. Winter sports
enthusiasts should learn to recognize the appearance of graupel and appreciate
the lightning risks associated with it.8
Although some studies show that campers, joggers, and other athletes are the
most common victims, others note work-related injuries in as many as 63% of
victims.6, 7 The chances of being struck may be increased by wearing or
carrying a metal object such as a helmet, rifle, umbrella, or golf club.9 Lightning
incidents often involve more than one victim when the current “splashes” to other
individuals or as ground current spreads the electrical power throughout the area
where a group may be sheltered in a storm.
PRINCIPLES OF DISEASE
Physics of Injury
The exact pathophysiology of electrical injury is not well understood because of
the large number of variables that cannot be measured or controlled when an
electrical current passes through tissue. With high-voltage injuries, most of the
injury appears to be thermal and most histologic studies reveal coagulation
necrosis consistent with thermal injury.10, 11 Lee et al 12 proposed the theory of
electroporation in which electrical charges too small to produce thermal damage
cause protein configuration changes that threaten cell wall integrity and cellular
function. The nature and severity of electrical burn injury are directly proportional
to the current strength, resistance, and duration of current flow
Box 1:
Electrothermal Heating Formulas
P =(I*I)Rt,
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and:
I =V/R
where:
P thermal power (heat), in Joules
I current, in amperes
R resistance, in ohms
t time, in seconds
V potential, in volts
Current strength is expressed in amperes and is a measure of the amount of
energy flowing through an object. Current is determined by the voltage and
resistance.13 Resistance is determined by the current’s pathway through the
body. The factors determining the severity of burn injury are summarized in Box
2.
Box 2:
Factors Determining Electrical Injury
Type of circuit
Duration
Resistance of tissues
Voltage
Amperage
Pathway of current
Type of Circuit
One of the factors affecting the nature and severity of electrical injury is the type
of circuit involved, either direct current (DC) or alternating current (AC).
High-voltage DC contact tends to cause a single muscle spasm, often throwing
the victim from the source. This results in a shorter duration of exposure but
increases the likelihood of traumatic blunt injury. Brief contact with a DC source
can also result in disturbances in cardiac rhythm, depending on the phase of the
cardiac cycle affected, the electrophysiologic principle used with cardiac
defibrillators.4
AC exposure to the same voltage tends to be three times more dangerous than
DC. Continuous muscle contraction, or tetany, can occur when the muscle fibers
are stimulated at between 40 and 110 times per second. Unfortunately, the
frequency of electrical transmission used in the United States is 60 Hz, which is
near the lowest frequency at which an incandescent light will appear to be
continuously lit.
The terms entry and exit are commonly used to describe electrical injuries. The
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terms source contact point and ground contact point, however, are more
appropriate when referring to AC injuries. The hand is the most common site of
contact via a tool that is in contact with an AC electric source. Since the flexors
of the hand and forearm are much stronger than the extensors, contraction of the
flexors at the wrist, elbow, and shoulder will occur, causing the hand grasping the
current source to pull the source even closer to the body. Currents greater than
the “let-go threshold” (6 to 9 mA) can prevent the victim from releasing the
current source, which prolongs the duration of exposure to the electrical current.
Resistance
Resistance is the tendency of a material to resist the flow of electric current; it is
specific for a given tissue, depending on its moisture content, temperature, and
other physical properties. The higher the resistance of a tissue to the flow of
current, the greater the potential for transformation of electrical energy to thermal
energy at any given current. Nerves, designed to carry electrical signals, and
muscle and blood vessels, because of their high electrolyte and water content,
have a low resistance and are good conductors. Bone, tendon, and fat, which all
contain a large amount of inert matrix, have a very high resistance and tend to
heat up and coagulate rather than transmit current. The other tissues of the body
are intermediate in resistance5, 14
Box 3:
Resistance of Body Tissues
Least
Nerves
Blood
Mucous membranes
Muscle
Intermediate
Dry skin
Most
Tendon
Fat
Bone
Skin is the primary resistor to the flow of current into the body. Skin on the inside
of the arm or back of the hand has a resistance of about 30,000 W/cm2. Deeply
calloused skin can have 20 to 70 times greater resistance.11
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Table 1:
Skin Resistance
Tissue
Tissue and Resistance
Mucous Membranes
100
Vascular Areas
Volar arm, inner thigh
300-10,000
Wet Skin
Bathtub
1200–1500
Sweat
2500
Other skin
10,000–40,000
Sole of foot
100,000–200,000
Heavily Calloused Palm
1,000,000–2,000,000
This high resistance may result in a significant amount of energy being expended
at the skin surface as the current burns its way through deep callous, resulting in
greater thermal injury to the skin but less internal damage than would be expected
if the current were delivered undiminished to the deep tissues. As the duration of
contact increases, however, the skin begins to blister and break down, resulting
in decreased resistance and a surge of current internally that can cause extensive
deep-tissue destruction. Moisture also lowers resistance. Sweating can decrease
the skin’s resistance to 2500 to 3000 ohms, and immersion in water causes a
further reduction to 1200 to 1500 ohms.
Amperage
Current, expressed in amperes, is a measure of the amount of energy that flows
through an object. As defined by Joule’s law, the heat generated is proportional
to the amperage squared.13 Amperage is dependent on the source voltage and
the resistance of the conductor and must normally be estimated. Although the
voltage of the source is often known, the resistance varies according to the
tissues involved. Additionally, as the tissue breaks down under the energy of the
current flow, its resistance may change markedly, making it difficult to predict the
amperage for any given electrical injury.
Table 2 shows the physical effects of different amperages at 50 to 60 Hz, which
is the AC frequency used in European countries and the United States.
Table 2:
Physical Effects of Different Amperage Levels at 50 to 60
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Hz
Physical effect
Milliamperes (mA)
Tingling sensation
1–4
Let-go current
Children
4
Women
7
Men
9
Freezing to circuit
10–20
Respiratory arrest from thoracic muscle tetany
20–50
Ventricular fibrillation
60–120
A very narrow range exists between the threshold of perception of current (0.2
to 0.4 mA) and let-go current (6 to 9 mA), the level above which a person
becomes unable to release the current source because of muscular tetany.
Thoracic tetany can occur at levels just above this let-go current and result in
respiratory arrest owing to paralysis of the muscles of respiration. Ventricular
fibrillation is estimated to occur at an amperage of 60 to 120 mA. Using skin
resistances from Table 1, contact with a 110-volt source with dry skin (10,000
to 40,000 W) results in current of 2.75 to 11 mA. Wet skin submerged in a
bathtub (1200 to 1500 W) subjected to the same household voltage results in a
current of 73–92 mA, that can cause electrocution with cardiac arrest but no
surface burns.
Duration of Contact
In general, the longer the duration of contact with high-voltage current, the
greater the electrothermal heating and degree of tissue destruction. Once
carbonization of tissue occurs, the resistance to current flow increases. The
physics are different with lightning. The extremely short duration and
extraordinarily high voltage and amperage of lightning both result in a very short
flow of current internally, with little, if any, skin breakdown and almost immediate
flashover of current around the body.
Voltage
Voltage is a measure of the difference in electrical potential between two points
and is determined by the electrical source. Electrical injuries are conventionally
divided into high or low voltage using 500 or 1000 V as the most common
dividing lines. Although both high and low voltage can cause significant morbidity
and mortality, high voltage results in greater current flow and therefore has a
greater potential for tissue destruction leading to major amputations and tissue
loss.
No deaths are recorded from contact with the low voltages associated with long
distance communications lines (24 V) or telephone lines (65 V). Death, however,
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is reported with exposure to 110 V household current, especially in special
environmental circumstances such as bathtub-related electrocutions.
Pathway
The pathway that a current takes determines the tissues at risk, the type of injury
seen, and the degree of conversion of electrical energy to heat. This is true
whether high, low, or lightning voltages are being considered. Current passing
through the heart or thorax can cause cardiac dysrhythmias and direct myocardial
damage. Current passing through the brain can result in respiratory arrest,
seizures, and paralysis. Current in proximity to the eyes can cause cataracts.
Current passing through the trunk of a body will cause less damage than if it
passes through a single digit. As current density increases, its tendency to flow
through the less-resistant tissues is overcome. Eventually it will flow through
tissues indiscriminately, as if the body were a volume conductor, with the
potential to destroy all tissues in the current’s path. Because the current is often
concentrated at the source and ground contact points, the greatest degree of
damage is often observed there. Nevertheless, extensive deep destruction of the
tissues may exist between these sites with high-voltage injuries, and the surface
damage is often only “the tip of the iceberg” for these injuries. Damage to the
internal structures of the body may be spotty, with areas of normal-appearing
tissue adjacent to burned tissue and with damage to structures at sites distant
from the apparent contact points. Although lightning is governed by the same
physical laws as artificial electricity, the rapid rise and decay of the energy makes
predicting the extent of lightning injury even more complicated than artificial
electrical injury. The most important difference between lightning and high-voltage
electrical injuries is the duration of exposure to the current.
Lightning is neither a direct current nor an alternating current. At best, it is a
unidirectional massive current impulse. Therefore lightning is classed as a current
phenomenon, rather than a voltage phenomenon. The cloud-to-ground lightning
impulse results from the breakdown of a large electric field between a cloud and
the ground, measured in millions of volts. Once connection is made with the
ground, this voltage difference between the cloud and ground disappears, and a
large current flows impulsively for a very short time. The study of such massive
discharges of such short duration is not well advanced, particularly with respect
to the effects on the human body.
Mathematical modeling of a lightning strike to the human body is substantiated on
animal models.5, 15 After lightning meets the body, current is initially transmitted
internally, after which skin breaks down, and ultimately external “flashover”
occurs. Experimental evidence suggests that “a fast flashover appreciably
diminishes the energy dissipation within the body and results in survival.”16
Although current may flow internally for an incredibly short time and cause
short-circuiting of electrical systems such as the heart, respiratory centers, and
autonomic nervous system, as well as spasm of arteries and muscles, it seldom
causes significant burns or tissue destruction.5, 17 Thus burns and myoglobinuric
renal failure are not a common injury pattern from lightning, whereas cardiac and
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respiratory arrest, vascular spasm, neurologic damage, and autonomic instability
play a much greater role.
Lightning tends to cause asystole rather than ventricular fibrillation. Although
cardiac automaticity may reestablish a rhythm, the duration of the respiratory
arrest may cause secondary deterioration of the rhythm to refractory ventricular
fibrillation and asystole.2, 5, 18 This secondary arrest occurs experimentally in
sheep.17 Other injuries caused by blunt trauma or ischemia from vascular
spasms, such as myocardial infarction or spinal artery syndromes, may
occasionally occur.19, 20, 21, 22, 23
Mechanisms of Injury
Electrical Injury
The primary electrical injury is burns. Secondary blunt trauma results from falls or
being thrown from the electrical source by an intense contraction of muscles.
Electrical burns can be classified into four different types.24
Box 4:
Types of Electrical Burns
Direct contact
Electrothermal heating
Indirect contact
Arc
Flame
Flash
Heating of tissues secondary to current causes electrothermal burns. Usually
these burns are a result of a low voltage shock with a limited affected area.
Severe electrothermal burns can occur, however, if a person grips a high voltage
conductor. The prolonged flow of current can result in significant burns anywhere
along the current path. Typically the skin lesions of electrothermal burns are
well-demarcated, deep-partial to full-thickness burns.
The most destructive indirect injury occurs when a victim becomes part of an
electrical arc. An electrical arc is a current spark formed between two objects of
differing potential that are not in contact with each other, usually a highly charged
source and a ground. Because the temperature of an electrical arc is
approximately 2500° C, it causes very deep thermal burns at the point where it
contacts the skin.14 In arcing circumstances, burns may be caused by the heat of
the arc itself, electrothermal heating due to current flow, or by flames that result
from the ignition of clothing. Instead of jumping in the form of a discrete arc
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causing contact point burns, current may jump the gap by splashing across the
entire body. These splash burns may cover a large portion of the body but are
generally only partial thickness.24
At the time of presentation, it is often difficult to determine the mechanism of
injury that caused an electrically injured patient’s burns. Electrothermal heating is
the main cause of muscle damage and is almost exclusively seen in high voltage
accidents with prolonged (seconds) contact and current flow.24
The histologic change seen in muscle injury that results from direct contact with
an electrical source is coagulation necrosis with shortening of the sarcomere.11,
14 Muscle damage can be spotty, so areas of viable and nonviable muscle are
often found in the same muscle group. Periosteal muscle damage may occur even
though overlying muscle appears to be normal. Similar to the muscle damage,
serious vascular damage usually occurs only after a high voltage accident.
Vascular damage is greatest in the media. This can lead to delayed hemorrhage
when the vessel eventually ruptures.2, 14, 25 Intimal damage may result in either
immediate or delayed thrombosis and vascular occlusion as edema and clots
form on the damaged internal surface of the vessel over a period of days.25 The
injury is usually most severe in the small muscle branches, where blood flow is
slower.26 This damage to small muscle arteries, combined with mixed muscle
viability that is not visible to gross inspection, creates the illusion of “progressive”
tissue necrosis.
Immediate arterial thrombosis will result in the absence of a pulse on initial
examination. The absence of a pulse, however, can also be due to transient
vascular spasm. Pulselessness resulting from vascular spasm should resolve within
a few hours. If pulselessness persists after this time, serious vascular injury is
likely.
Damage to neural tissue may also occur via several mechanisms. A nerve may
demonstrate an immediate drop in conductivity as it undergoes coagulation
necrosis similar to that observed in muscle. In addition, it may suffer indirect
damage as its vascular supply or myelin sheath is injured or as progressive edema
results in a compartment syndrome. The signs of neural damage may develop
immediately or be delayed hours to days. Since the skull is a common contact
point, the brain is commonly injured. Histologic studies of the brain reveal focal
petechial hemorrhages in the brain stem, cerebral edema, and widespread
chromatolysis (the disintegration of chromophil bodies of neurons).14
Exposure to electricity may cause immediate death from asystole, ventricular
fibrillation, or respiratory paralysis, depending on the voltage and pathway.
Lightning Injury
Lightning injury may occur by five mechanisms.
Box 5:
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Electrical and Lightning Injuries
Mechanisms of Lightning Injury
Direct strike
Orifice entry
Contact
Side flash, “splash”
Ground current or step voltage
Blunt trauma
The mechanism of injury with a direct strike is self-evident. It has been
substantiated experimentally in sheep that lightning strikes near the head may
enter orifices such as the eyes, ears, and mouth to flow internally.17, 19, 27 This
may help explain the myriad eye and ear symptoms and signs that are reported
with lightning injury.
Injury from contact occurs when the person is touching an object that is part of
the pathway of lightning current, such as a tree or tent pole. Side flash or splash
occurs as lightning jumps from its primary strike object to a nearby person on its
way to ground.21, 28, 29 Step voltage, a difference in electrical potential
between a person’s feet, may occur as lightning current spreads radially through
the ground. A person is a far better conductor of electricity than the earth. Thus a
person who has one foot closer than the other to the strike point will have a
potential difference between the feet so that the lightning current will preferentially
flow through the legs and body rather than the ground. This is a common killer of
large livestock such as cattle and horses because of the distance between their
hind legs and forelegs.30
Blunt injury from lightning can occur from two mechanisms. First, the person may
be thrown a considerable distance by the sudden, massive contraction caused by
current passing through the body. Second, an explosive or implosive force occurs
as the lightning pathway is instantaneously superheated and then rapidly cooled
following the passage of the lightning. The heating is seldom long enough to cause
severe burns but does cause rapid expansion of air followed by rapid implosion
of the cooled air as it rushes back into the void.5
CLINICAL FEATURES
High-voltage injury patients commonly present with devastating burns requiring
prolonged hospitalization with multiple complications. Lightning and low-voltage
injury patients may have little evidence of injury or, alternatively, may be in
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Electrical and Lightning Injuries
cardiopulmonary arrest. After the initial resuscitation of lightning and low-voltage
injury patients, other conditions may be identified. These patients may have
significant residual morbidity from pain syndromes or brain damage that is similar
to that suffered with blunt head injury.31, 32, 33, 34, 35
Head and Neck
Electrical Injury
The head is a common point of contact for high-voltage injuries, and the patient
may exhibit burns as well as neurologic damage. Cataracts develop in
approximately 6% of cases of high-voltage injuries, especially whenever electrical
injury occurs in the vicinity of the head.36 Although cataracts may be present
initially or develop shortly after the accident, they more typically appear months
after the injury. Visual acuity and funduscopic examination should be performed
at presentation. Referral to an ophthalmologist familiar with electrical cataract
formation may be necessary.
Lightning Injury
Lightning strikes may cause skull fractures and cervical spine injury from
associated blunt trauma.21, 22, 37 Tympanic membrane rupture is commonly
found in lightning victims and may be secondary to the shock wave, a direct burn,
or a basilar skull fracture.5, 18, 38 Although most patients recover without
serious sequelae, disruption of the ossicles and mastoid may occur, as well as
cerebrospinal fluid otorrhea, hemotympanum, and permanent deafness.18, 38
Injuries to the eyes include corneal lesions, uveitis, iridocyclitis, hyphema, vitreous
hemorrhage, optic atrophy, retinal detachment, and choroidoretinitis. As a result,
dilated, unreactive pupils are not a reliable indicator of death.39 As with electrical
injuries, cataracts may develop later in some patients.5, 18, 40
Cardiovascular System
Electrical Injury
Cardiac arrest, either from asystole or ventricular fibrillation, is a common
presenting condition in electrical accidents. Other electrocardiographic (ECG)
findings include sinus tachycardia, transient ST segment elevation, reversible QT
segment prolongation, premature ventricular contractions, atrial fibrillation, and
bundle branch block.2, 41 Acute myocardial infarction is reported but is
relatively rare.42, 43 Damage to skeletal muscles may produce a rise in the
CPK-MB fraction, leading to a spurious diagnosis of myocardial infarction in
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some settings.43, 44
Lightning Injury
In lightning injury, cardiac damage or arrest may be caused by either the electrical
shock or induced vascular spasm.20, 45 Numerous dysrhythmias are reported in
the absence of cardiac arrest.5, 14 Nonspecific ST-T wave segment changes
and prolongation of the QT interval may occur, and serum levels of cardiac
enzymes are often elevated.5, 46, 47 Hypertension is commonly present initially
with lightning injury but usually resolves without treatment within a few hours.
Skin
Electrical Injury
Other than cardiac arrest, the most devastating injuries that accompany an
electrical injury are burns, which are most severe at the source and ground
contact points. The most common sites of contact with the source include the
hands and the skull. The most common areas of ground are the heels. A patient
may have multiple source and ground contact points. Burns in severe electrical
accidents often appear as painless, depressed, yellow-gray, punctate areas with
central necrosis, or the areas may be mummified.14 High-voltage current often
flows internally and can create massive muscle damage. If contact was brief,
however, minimal flow may have occurred and the visible skin damage may
represent nearly all of the damage. One should not attempt to predict the amount
of underlying tissue damage from the amount of cutaneous involvement.
A peculiar type of burn associated with electrical injury is the “kissing burn,”
which occurs at the flexor creases.14 As the current causes flexion of the
extremity, the skin of the flexor surfaces at the joints touches. Combined with the
moist environment that often occurs at the flexor areas, the electric current may
arc across the flexor crease, causing arc burns on both flexor surfaces and
extensive underlying tissue damage.
Electrical flash burns are usually superficial partial-thickness burns, similar to
other flash burns. Isolated thermal burns may also be seen when clothing ignites.
The total body surface area affected by burns in electrical injury averages 10% to
25%. Severe burns to the skull, and occasionally to the dura, are reported.48, 49
The most common electrical injury seen in children less than 4 years of age is the
mouth burn that occurs from sucking on a household electrical extension cord.4
These burns usually represent local arc burns, may involve the orbicularis oris
muscle, and are especially worrisome when the commissure is involved because
of the likelihood of cosmetic deformity. A significant risk of delayed bleeding
from the labial artery exists when the eschar separates. Damage to developing
dentition is reported, and referral to an oral surgeon familiar with electrical injuries
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Electrical and Lightning Injuries
is recommended.50
Lightning Injury
Deep burns occur in fewer than 5% of lightning injuries.18, 51 Patients may
exhibit one or more of four types of superficial burns or skin changes that do not
reflect actual burn injury: linear, punctate, feathering, or thermal burns.5, 12, 18,
51, 52, 53
Linear burns tend to occur in areas where sweat or water accumulate, such as
under the arms or down the chest. These are superficial burns that appear to be
caused by steam production from the flashover phenomenon. Punctate burns
appear as multiple, small cigarette-like burns, often with a heavier central
concentration in a rosette-like pattern.52 They range from a few millimeters to a
centimeter in diameter and seldom require grafting.
Feathering burns are not true burns because there is no damage to the skin
itself.51 They seem to be caused by electron showers induced by the lightning
that make a fern pattern on the skin.51, 52, 53 These transient lesions are
pathognomonic for lightning injury and require no therapy.54 Thermal burns
occur if the clothing is ignited or may be caused by metal that the person is
wearing or carrying during the flashover.24
Extremities
Electrical Injury
In high-voltage injuries, muscle necrosis can extend to sites distant from the
observed skin injury, and compartment syndromes occur as a result of vascular
ischemia and muscle edema. Decompression fasciotomy or amputation is often
necessary because of extensive tissue damage.55, 56 Massive release of
myoglobin from the damaged muscle may lead to myoglobinuric renal failure.
Vascular damage from the electrical energy may become evident at any time.25,
26 Pulses and capillary refill should be assessed and documented in all
extremities, and neurovascular checks should be repeated frequently. Because
the arteries are a high-flow system, heat may be dissipated fairly well and cause
little apparent initial damage but result in subsequent deterioration. The veins, on
the other hand, are a low-flow system, allowing the heat energy to cause more
rapid heating of the blood, with resulting thrombosis. Consequently, an extremity
may appear edematous initially. With severe injuries, the entire extremity may
appear mummified when all tissue elements, including the arteries, suffer
coagulation necrosis.
Damage to the vessel wall at the time of injury may also result in delayed
thrombosis and hemorrhage, especially in the small arteries to the muscle.25, 26
This ongoing vascular damage can cause a partial-thickness burn to develop into
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Electrical and Lightning Injuries
a full-thickness burn as the vascular supply to the area diminishes. Progressive
loss of muscle because of vascular ischemia downstream from damaged vessels
may mandate repeated deep debridements.26
Lightning Injury
Lightning injury may cause transient vasospasm so severe that the extremities
appear cold, blue, mottled, and pulseless. This usually resolves within a few hours
and rarely requires vascular imaging or surgical intervention.4, 18
Skeletal System
Fractures of most of the long bones caused by the trauma associated with
electrical injury are reported.59, 60 Both posterior and anterior shoulder
dislocations caused by tetanic spasm of the rotator cuff muscles are also
reported, as well as spinal fractures. As with electrical injury, numerous types of
fractures and dislocations are reported with lightning injury.5
Nervous System
Electrical Injury
In high-voltage injuries, loss of consciousness may occur but is usually transient
unless there is a significant concomitant head injury. Prolonged coma with
eventual recovery is also reported. Patients may exhibit confusion, flat affect, and
difficulty with short-term memory and concentration.31, 32, 33, 34, 35, 59
Electrical injury to the central nervous system (CNS) may cause a seizure, either
as an isolated event or as part of a new-onset seizure disorder.59 Other possible
causes of seizures, such as hypoxia and traumatic CNS injury, should be
considered. Neurologic symptoms may improve, but long-term disability is
common. Lower extremity weakness is commonly undiagnosed until ambulation
is attempted.60
In high-voltage exposures, spinal cord injury may result from fractures or
ligamentous disruption of the cervical, thoracic, or lumbar spine.60, 61, 62
Neurologic damage in patients without evidence of spinal injury seems to follow
two patterns, immediate and delayed. Patients with immediate damage have
symptoms of weakness and paresthesias develop within hours of the insult.59
Lower extremity findings are more common than upper extremity findings. These
patients have a good prognosis for partial or complete recovery. Delayed
neurologic damage may present from days to years after the insult. The findings
usually fall into three clinical pictures: ascending paralysis, amyotrophic lateral
sclerosis, or transverse myelitis.62 Motor findings predominate. Sensory findings
are also common, but they may be patchy and may not match the motor levels.
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Electrical and Lightning Injuries
Although recovery is reported, the prognosis is usually poor.60
Lightning Injury
On initial presentation, up to two thirds of the seriously injured lightning patients
have keraunoparalysis, which is a unique temporary paralysis secondary to
lightning strike. It is characterized by lower and sometimes upper extremities that
are blue, mottled, cold, and pulseless. These findings are secondary to vascular
spasm and sympathetic nervous system instability.18, 63 Generally this clears
within a few hours, although some patients may be left with permanent paresis or
paresthesias.
Paraplegia, intracranial hemorrhages, cardiac enzyme elevations, seizures, and
electroencephalogram (EEG) changes are reported after lightning injuries.5, 46,
47, 62, 63, 64, 65, 66 Loss of consciousness for varying periods is common,
and confusion and anterograde amnesia are almost universal findings.18, 67
Peripheral nerve damage is common, and recovery is usually poor.68, 69 A
syndrome of delayed muscle atrophy caused by electrical injury of the nerves is
described, even in the absence of cutaneous burns.70
Other Viscera
Electrical Injury
Injury to the lungs may occur because of associated blunt trauma but is rare from
electrical current, perhaps because air is a poor conductor. Injury to solid
visceral organs also is rare, but damage to the pancreas and liver is reported.71
Injuries to hollow viscera, including the small intestine, large intestine, bladder,
and gallbladder, are also reported.71,72
Lightning Injury
Pulmonary contusion and hemorrhage are reported with lightning injury.22, 73
Blunt abdominal injuries occur rarely.5 None of the other intraabdominal
catastrophes commonly associated with high-voltage electrical injury such as
gallbladder necrosis or mesenteric thrombosis are seen with lightning injury.
Other Low-Voltage Injuries
An accurate history is essential to ensure that an apparent low-voltage injury was
not caused by the discharge from a capacitor (as in the repair of a television,
microwave oven, or computer monitor) or other high-voltage source. Although
burns from low-voltage sources are usually less severe than those from
high-voltage sources, patients may still complain of paresthesias for an extended
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Electrical and Lightning Injuries
period, experience cardiac dysrhythmias, or have cataracts develop if the shock
occurs close to the face or head.4
Complications
Electrical Injury
Cardiac arrest generally occurs only at the initial presentation or as a final event
after a long and complicated hospital course. Many of the complications are
similar to those of thermal burns and crush injuries, including infection, clostridial
myositis, and myoglobinuria. The incidence of acute myoglobinuric renal failure
has decreased since the widespread adoption of aggressive alkalinized fluid
resuscitation. Fasciotomies or carpal tunnel release may be necessary for
treatment of compartment syndromes.55, 56 Tissue loss and major amputations
are common with severe high-voltage injuries and result in the need for extensive
rehabilitation.
Neurologic complications such as loss of consciousness, peripheral nerve
damage, and delayed spinal cord syndromes may occur.35, 59, 60, 61, 62, 69
Damage to the brain may result in a permanent seizure disorder.37 Long-term
neuropsychiatric complications include depression, anxiety, inability to continue in
the same profession, aggressive behavior, and suicide.74 Stress ulcers are the
most common gastrointestinal complication after burn ileus. Abdominal injuries
from ischemia, vascular damage, burns, or associated blunt trauma may be
overlooked initially.14, 71, 72 The most common causes of hospital mortality are
pneumonia, sepsis, and multisystem organ failure.
Lightning Injury
Complications of lightning injury fall into three areas: (1) those that could be
reasonably predicted from the presenting signs and can be treated routinely, such
as hearing loss from tympanic membrane rupture or paresthesias and paresis
from neurologic damage, (2) long-term neurologic deficits similar to those
suffered with blunt head injury and chronic pain syndromes, and (3) iatrogenic
complications that are secondary to overaggressive management.
In the past, patients with lightning injuries were often treated like those with
high-voltage electrical injuries. These injuries, however, are distinctly different.
The treatment of lightning victims seldom requires massive fluid resuscitation,
fasciotomies for compartment syndromes, mannitol and furosemide diuretics,
alkalinization of the urine, amputations, or large repeated debridements.5, 18, 21,
46
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Electrical and Lightning Injuries
DIFFERENTIAL CONSIDERATIONS
Electrical Injury
Electrical injuries are usually self-evident from historical surroundings, except in
the case of bathtub accidents, instances when no burns occur, or foul play. It is
important to determine the mechanism of burn injury because flash burns have a
much better prognosis than arc or conductive burns. Alterations in consciousness
or seizures can be caused by the electrical injury or result from an associated
traumatic brain injury.
Lightning Injury
The differential diagnosis of lightning injury is more complex, often because the
incident is unobserved. It includes many of the causes of unconsciousness,
paralysis, or disorientation of unclear etiology.5
Box 6:
Differential Diagnosis of Lightning Injuries
Cardiac dysrhythmias
Myocardial infarction
Cerebrovascular accident
Subarachnoid hemorrhage
Seizures
Closed-head injury
Spinal cord trauma
Evidence of a thunderstorm or a witness to the lightning strike may not be
available, particularly when victims are alone when injured. The presence of
typical burn patterns, such as feathering, may be helpful.
MANAGEMENT
Prehospital
Securing the Scene
When first reaching the scene, prehospital personnel should secure the area so
that bystanders and rescuers do not sustain other injuries. For high-voltage
incidents, the power source must be turned off. Although many approaches to
achieving this goal are recommended, the safest approach is to involve the local
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Electrical and Lightning Injuries
power company in high-voltage accidents. Accidents involving discrete electrical
sources that are easily disconnected through a circuit box or switch are easier to
manage, although rescuers should still ensure that the power is off before
approaching the victim. The use of electrical gloves by emergency medical
service (EMS) personnel is very dangerous. A microscopic hole in a glove can
result in an explosive injury to the hand inside it, as thousands of volts from the
circuit concentrate there to enter the glove.
Although a line may be on the ground and appear to be dead, it may have
substantial current from it pouring into the ground. This current spreads out in a
circle along and just below the surface of the ground, so the area remains
electrified and dangerous, a phenomenon known as ground current. Even if the
line is dead, automatic circuit reclosers may repower the line resulting in
successive surges of current.75 Therefore rescue vehicles should park at least
one entire span away from the line.
In lightning incidents, pre-hospital personnel must remember that lightning can
strike the same place twice and guard themselves against also becoming victims
with appropriate and timely evacuation measures.
Triage Considerations
Field evaluation of patients may involve triage of multiple victims. Traditional rules
of mass casualty triage do not apply to lightning victims. The major cause of
death in lightning injuries is cardiorespiratory arrest. 18 In the absence of
cardiopulmonary arrest, victims are highly unlikely to die of any other cause.18
Thus triage of lightning victims should concentrate on those who appear to be in
cardiorespiratory arrest. Cardiopulmonary resuscitation should be started on
those who have no pulse or respirations. When multiple victims are involved, the
evaluation of those who are breathing may be delayed because they are likely to
survive the incident.
For practical purposes, lightning acts as a massive DC countershock that results
in asystole.5 Although intrinsic cardiac automaticity may resume cardiac activity,
the respiratory arrest caused by CNS injury often lasts longer than the cardiac
pause and may lead to a secondary cardiac arrest with ventricular fibrillation from
hypoxia.6, 14, 17 If the victim is properly ventilated during the time between the
two arrests, the second arrest may theoretically be avoided.
Initial Resuscitation
Electrical injury victims may require a combination of cardiac and trauma care
because they often suffer blunt injuries and burns as well as possible cardiac
damage. Spinal immobilization is indicated whenever associated spinal trauma is
suspected. Fractures and dislocations should be splinted, and burns should be
covered with clean, dry dressings.
All patients with conductive injury should have at least one large-bore intravenous
(IV) line established. An electrical injury should be treated like a crush injury,
rather than a thermal burn, because of the large amount of tissue damage that is
often present under normal-appearing skin. As a result, none of the formulas for
IV fluids based on percentage of burned body surface area are reliable.
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Electrical and Lightning Injuries
Hypotensive patients should initially receive a bolus of 20 ml/kg of isotonic fluid,
and subsequent fluid management then based on the patient’s vital signs and
clinical status.
ED
Assessment
The victim of an electrical injury may not be able to give an adequate history,
either because of the severity of injury and accompanying shock and hypoxia or
because of unconsciousness or confusion that often accompanies less severe
injuries. The history obtained from bystanders and the paramedics regarding the
type of electrical source, duration of contact, environmental factors at the scene,
and resuscitative measures provided can be helpful.
Resuscitative efforts should be continued in the ED with adequate fluid
administration and insertion of a Foley catheter for patients with high-voltage
injury and extensive burns. Fluids should be administered at a rate sufficient to
maintain a urine output of at least 0.5 to 1.0 ml/kg/hr in the absence of heme
pigment in the urine and 1.0 to 1.5 ml/kg/hr in its presence.
Cardiac monitoring is indicated for severely injured patients and for those who
have the indications listed in Box 7.76
Box 7:
Indications for Electrocardiographic Monitoring
Cardiac arrest
Documented loss of consciousness
Abnormal ECG
Dysrhythmia observed in prehospital or ED setting
History of cardiac disease
Presence of significant risk factors for cardiac disease
Concomitant injury severe enough to warrant admission
Suspicion of conductive injury
Hypoxia
Chest pain
All high-voltage injury victims and low-voltage victims with cardiorespiratory
complaints should have an ECG and cardiac isoenzyme determinations. Although
ECG changes and dysrhythmias are common with electrical injuries, anesthesia
and surgical procedures performed in the first 48 hours of care can be
accomplished without cardiac complications.76, 77 The patient’s clinical status
should guide the use of invasive monitoring with central venous pressure
catheters, intracranial pressure monitors, and Swan-Ganz catheters.5, 78
Victims of electrical injury with altered mentation should have a computed
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Electrical and Lightning Injuries
tomography (CT) scan performed. Most lightning victims will behave as though
they have had electroconvulsive therapy, with confusion and anterograde amnesia
for several days. If any neurologic deterioration occurs after an electrical injury, a
CT scan is indicated to assess for intracranial hemorrhage.18, 66
Lightning victims who do not suffer cardiopulmonary arrest at the time of the
strike generally do well with supportive therapy. Those who have
cardiopulmonary arrest may have a poor prognosis, particularly if there is
hypoxic brain damage.5, 6, 76
Ancillary Tests
Electrical Injury
The laboratory evaluation of the patient sustaining an electrical injury depends on
the extent of injury. All patients with evidence of conductive injury or significant
surface burns should have the following laboratory tests: complete blood count
(CBC), electrolyte levels, serum myoglobin, blood urea nitrogen (BUN), serum
creatinine, and urinalysis. Patients with severe electrical injury or suspected
intraabdominal injury should also have obtained pancreatic and hepatic enzymes
and coagulation profile.41 The clinician should consider ordering a type and
cross-match, particularly if major debridements may be necessary. Arterial blood
gas analysis is indicated if the victim needs ventilatory intervention or alkalinization
therapy.
All patients should be evaluated for myoglobinuria, a common complication of
high voltage electrical injury. If the urine is pigmented or the dipstick examination
of the urine is positive for blood, and no red blood cells (RBCs) are seen on
microscopic analysis, assume the patient has myoglobinuria and treat accordingly.
Creatine kinase (CK) levels should be drawn and isoenzyme analysis performed.
Peak CK levels are shown to predict the amount of muscle injury, risk of
amputation, and length of hospitalization; the clinical value of a single level in the
acute setting, however, is not established. Cardiac enzyme levels should be
interpreted with care when diagnosing myocardial infarction in the setting of
electrical injury. The peak CK level is not indicative of myocardial damage in
electrical injury because of the large amount of skeletal muscle injury. Skeletal
muscle cells damaged by electrical current can contain as much as 20% to 25%
CK-MB fraction, suggesting injured skeletal muscle rather than myocardial injury
as a possible source of an elevated CK-MB fraction.44 CK-MB fractions, ECG
changes, thallium studies, angiography, and echocardiography correlate poorly in
acute myocardial infarction following electrical injury. Other cardiac enzymes
(such as troponin) are not well studied in electrical injury but may prove useful in
determining myocardial injury.
All patients sustaining an electrical injury should receive cardiac monitoring in the
ED and an ECG despite the source voltage. Indications for admission for
electrocardiographic monitoring are listed in Box 7.41, 76
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Electrical and Lightning Injuries
Radiographs of the cervical spine should be performed if spinal injury is clinically
suspected. Radiographs of any other areas in which the patient complains of pain
or has an apparent deformity should be performed. Angiography is not shown to
be useful in the planning of debridements or amputations and is not routinely
indicated.26 Technetium pyrophosphate scanning to detect areas of clinically
unsuspected myonecrosis can be useful.45, 55 Nonviable muscle will appear as
cold spots on the scan, lacking the normal level of uptake. Hot spots on the scan
may consist of 20% to 80% viable muscle and should be followed clinically.55,
79, 80 CT or magnetic resonance imaging may be useful in the evaluation of
associated trauma and are essential for evaluation of possible intracranial injuries,
particularly if the Glasgow Coma Scale score does not progressively improve.
Lightning Injury
In patients injured by lightning an ECG should be obtained. Serum markers for
cardiac injury are indicated in patients with chest pain, abnormal ECGs, or
altered mentation. The severity or nature of the victim’s injuries may require other
laboratory studies. Radiographic studies, particularly CT scan of the head, may
be indicated, depending on the patient’s level of consciousness at presentation
and throughout the evaluation and treatment.
Specific Therapies
Rhabdomyolysis
Patients with heme pigment in the urine should be assumed to have myoglobinuria
until the diagnosis can be excluded by more specific testing. Alkalinization of the
urine increases the solubility of myoglobin in the urine, increasing the rate of
clearance. Urine output should be maintained at 1.0 to 1.5 ml/kg/hr until all traces
of myoglobin have cleared from the urine while the blood is maintained at a pH of
at least 7.45 using sodium bicarbonate. Furosemide or mannitol may be used to
cause further diuresis. The recommended dose of mannitol is 25 g initially,
followed by 12.5 g/kg/hr, titrated as needed to maintain urine flow greater than
50 ml/hr. Unlike with high-voltage injuries, rhabdomyolysis is rare with lightning
injuries.
Burn Wound Care
Cutaneous burns should be dressed with antibiotic dressings, such as sulfadiazine
silver (Silvadene). Mafenide acetate (Sulfamylon) is occasionally used for
selected burns; however, its use may result in electrolyte abnormalities because of
its carbonic anhydrase inhibitory activity.
Electrical burns are especially prone to tetanus, and patients should receive
Page 21
Electrical and Lightning Injuries
tetanus toxoid and tetanus immune globulin on the basis of their immunization
history. Clostridial myositis is common, but prophylactic administration of
high-dose penicillin to prevent clostridial myonecrosis is controversial and should
not be used without discussion with the managing surgeon or burn unit. In
general, systemic antibiotics are not used unless culture or biopsy proves infection
is present.
Extremity Injuries
Current management of electrical injuries of the extremities favors early and
aggressive surgical management, including early fasciotomy, carpal tunnel release,
or even amputation of an obviously nonviable extremity.56, 81
Extremities should be splinted in a functional position to minimize edema and
contracture formation. The hand should be splinted in 35- to 45-degree extension
at the wrist, 80- to 90-degree flexion at the metacarpophalangeal joints, and
almost full extension at the proximal and distal interphalangeal joints. This position
minimizes edema formation. During the first several days of hospitalization,
frequent monitoring of the neurovascular status of all extremities is essential.
DISPOSITION
Electrical Injuries
Transfer to Burn Center
Most patients with significant electrical burns should be stabilized and transferred
to a regional burn center for burn care and extensive occupational and physical
rehabilitation. These severely injured victims and their families may benefit from
counseling because of the extensive life changes that occur consequent to the
injury.
Admission
Indications for admission for electrocardiographic monitoring are listed in Box 7.
In general, when corporal conduction is suspected, the patient should be
admitted for 12 to 24 hours of cardiac monitoring.
Outpatient Management
Patients who are totally asymptomatic and have a normal physical examination
after low-voltage exposure can be reassured and then discharged without
performing any ancillary tests.82 Those patients with cutaneous burns or mild
persistent symptoms can be discharged if they have a normal ECG and no urinary
heme pigment. The ED physician should provide out-patient referral in the event
that current symptoms persist or new symptoms (delayed cataracts, weakness,
or paresthesias) develop.
Electrical injury during pregnancy from low-voltage sources is reported to result
Page 22
Electrical and Lightning Injuries
in stillbirth. A prospective cohort study of women receiving electric shock in
pregnancy suggests that accidental electric shock usually does not pose a major
fetal risk.83 Nevertheless, obstetric consultation or referral is advisable for all
pregnant patients reporting electrical injury, regardless of symptomatology at the
time of presentation. Placental abruption, the most common cause of fetal death
after blunt trauma, may result from even minor trauma such as may be associated
with electrical injuries. Patients in the latter half of pregnancy should receive fetal
monitoring if there has been even minor blunt trauma and be considered high-risk
patients for the remainder of their pregnancy.84, 85 First-trimester patients
should be informed of the remote risk of spontaneous abortion and, if no other
indications for admission exist, may be discharged with instructions for threatened
miscarriage and close obstetric follow-up evaluation. The prognosis for fetal
survival after lightning strike varies.5, 18
Pediatric patients with oral burns may generally be safely discharged if close adult
care is assured. There is no evidence that an isolated oral burn correlates with
cardiac injury or myoglobinuria. In general, these patients require surgical and
dental consultation for oral splinting, eventual debridement, and occasionally
reconstructive surgery. After appropriate consultation, if hospitalization is not
deemed necessary, the child’s parents should be warned about the possibility of
delayed hemorrhage and receive instructions to apply direct pressure by pinching
the bleeding site and to immediately return to the ED.
Lightning Injuries
Many of the signs of lightning injuries, such as lower extremity paralysis and
mottling and confusion and amnesia, resolve with time. After spinal cord and
intracranial processes are excluded, observation is the mainstay of treatment.
Consultation with other specialists may be indicated for otic and ophthalmic
damage, although these are usually not emergent considerations. More severely
injured lightning patients require both trauma surgeon and cardiology
consultations, although with lightning injuries medical pathology predominates. If
there is a history of loss of consciousness or if the patient exhibits confusion,
hospital admission and observation are suggested. After evaluation, if the ECG is
normal, asymptomatic patients (including those with feathering burns) may be
discharged home with referral for follow up from ophthalmology and other
specialties as indicated.
KEY CONCEPTS
· Exposure to AC is three times more dangerous than DC of the same voltage
because of the potential for muscular tetany and prolonged contact.
Page 23
Electrical and Lightning Injuries
· Nerves, muscles, and blood vessels have low resistance and are better electrical
conductors than bone, tendon, and fat.
· Electrical burns are usually most severe at the source and ground contact points.
It is not possible to predict the amount of underlying tissue damage based on the
amount of cutaneous involvement.
· Traditional rules of triage do not apply to lightning victims. Triage of lightning
victims should concentrate on those who appear to be in cardiorespiratory arrest.
· The most common presenting signs of lightning injury (keraunoparalysis,
mottling, confusion, amnesia) resolve with time. After spinal cord and intracranial
processes are excluded, observation is the mainstay of treatment.
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